> ## Documentation Index > Fetch the complete documentation index at: https://docs.phylax.systems/llms.txt > Use this file to discover all available pages before exploring further. # Circuit breakers > Overview of cumulative and rate-of-change circuit breakers for ERC20 balance changes Circuit breakers enforce configured limits on ERC20 balance changes. They can reject a candidate transaction before it settles. This page compares cumulative and rate-of-change controls. ## What they watch * **Adopter:** The contract protected by the assertion. * **Token:** The ERC20 balance being watched. * **Direction:** Tokens entering or leaving the adopter. * **Time:** Balance changes across blocks and transactions. ## Circuit breaker types Limits net tokens leaving the adopter over a rolling window. Limits net tokens entering the adopter over a rolling window. Lets an assertion limit how quickly the watched balance changes. ## How cumulative and rate limits work together Cumulative and rate-of-change limits use different semantics. A cumulative limit measures total net flow over a rolling window, while a rate limit measures how quickly the balance changes. An assertion can enforce either policy or both. Both policies use a matching cumulative watcher to invoke the assertion. For a rate limit, the assertion reads the rolling-window rate data during that callback. | Risk | Circuit breaker | | ---------------------------------------------- | ----------------------------- | | Too many tokens leave over time | Cumulative outflow | | Too many tokens enter over time | Cumulative inflow | | The balance changes too quickly | Rate of change | | Total flow and flow speed must both be bounded | Cumulative and rate of change | When checks are combined, the assertion can reject a transaction when either limit is exceeded. ## Why use a Phylax circuit breaker A protocol-integrated circuit breaker protects the execution paths wired through it. A Phylax circuit breaker runs as an assertion before the transaction settles. It watches the actual ERC20 balance change of the adopter. | | Protocol-integrated circuit breaker | Phylax circuit breaker | | ------------- | ----------------------------------------------------- | -------------------------------------------------------------- | | Coverage | Covers paths integrated with the breaker | Covers observed changes to the adopter's watched ERC20 balance | | Measurement | Defined by the protocol integration | Uses the observed balance change | | Time window | May require counters or buckets in protocol storage | Keeps rolling buckets outside the protected protocol | | Protocol code | Adds hooks, state, and audit surface | Adds no breaker code or storage to the protocol | | User gas | May include breaker calls and storage writes | Adds no protocol-side gas for breaker accounting | | Changes | Integration may require a protocol upgrade or wrapper | Uses an assertion release without changing protocol code | Because enforcement runs as an assertion, the protocol does not need breaker-specific hooks or storage. The assertion can reject a candidate transaction when it exceeds the configured policy. ## Monitoring and incident response Circuit breakers constrain token flow rather than a specific attack path, so they can limit the impact of different exploit classes, including attacks that begin with oracle manipulation. They bound flow within the configured rolling window; they do not replace monitoring or incident response. Choose a window long enough for your team to receive an invalidation alert, investigate, and apply mitigation before earlier flow ages out of the window. Before production, [validate the threshold and window in staging](../../credible/testing-strategy#monitor-staging-behavior) and [configure invalidation notifications](../../credible/dapp-integrations).